The present embodiments relate to detecting ionizing radiation.
Nuclear medicine senses radiation emission to acquire images that show the function and/or physiology of organs, bones or tissues of the body. Radiopharmaceuticals are introduced into the body by injection or ingestion. These radiopharmaceuticals are then found in specific target organs, bones, or tissues of interest. The radiopharmaceuticals cause gamma photons to radiate from the body, which are then captured by detectors. The interactions of the gamma photons with scintillation crystals of the detectors produce flashes of light. The light is detected by an array of optical sensors in each detector.
Positron emission tomography (PET) is a nuclear medicine imaging technique that uses positron emitting radionuclides. PET is based on coincidence detection of two gamma photons produced from single positron-electron annihilation. The two gamma photons travel in opposite directions from the annihilation site, and can be detected by two opposing detectors of a ring of detectors. Annihilation events are typically identified by a time coincidence in the detection of the two gamma photons. The opposing detectors identify a line-of-response (LOR) along which the annihilation event occurred.
The quality of PET images is improved when the timing resolution allows a more detailed comparison of the arrival times of the two gamma photons. Some PET systems use the comparison to determine the time of flight of each gamma photon from the annihilation site. So called time-of-flight PET systems use the time-of-flight information to determine where along the line of response the annihilation occurred. The annihilation site is thus located more accurately, improving the PET image.
Regardless of the approach, actual detection of the gamma radiation is needed. The interaction of the gamma photons with a scintillation crystal of the detector produces a flash of light, but the clarity and/or quality of the detection may be improved.